Flotation process for metallic separation



l2, TQZZO stares CHARLES H. FORREST, 0F BAHWAY, NEW JERSEY, ASSIGNOR TO THE BARBER ASPHALT PAVING COMPANY, OF PHILADELPHIA,PENIQQYLVANIA, A 30181 0- BATIGN OF WEST VIRGINIA.

FLOTATION PROCESS FOR METALLIC SEPARATION.

N0 Drawing.

To all 2.0 from it may concern Be it known that I, CHanLEs N. FORREST, a citizen of the United States, residing at Rahway, in the countyof Union and State of New Jersey, have invented certain new and useful Improvements in Flotation Processes for Metallic Separation, whereof the following is aspecification.

My invention comprises a novel flotation process for metallic separation, characterized by the use of a liquid hydrocarbon distillate from the solid native bitumen known as gilsonite. This present application is a. continuation in part of my prior application, Serial No. 195,721. of October 10, 1917, entitled Liquid hydrocarbon, and is filed pursuant to a requirement for division of said prior application made by the United States Patent Oflice under Rule 42 of its Rules of Practice.

The flotation process consists essentially in mixing pulverized metallic: ores with water and oil,-or, more commonly, with water and a mixtureof different oils-and then frothing such mixture by agitating or aerating it. The froth collects the metallic particles and rises to the surface of the mixture, while the gangue of non-metallic particles sinks to the bottom. The floating metal-bearing: froth flows off fromt'the mixing tank and is treated elsewhere in a suitable manner for the recovery of its metal constituents. The etliciency of any particular oil (or mixture of oils) in flotation is determined, therefore, by the amount of metal it removes from the gangrue. As flotation or froth-producing reagents, there have hitherto been used oils produced in the distillation of petroleum; coal or wood tars or products; and mixtures of petroleum or creosote with pine oil or eucalyptus oil.

Diflerent kinds of metallic ores have been found to require different oil mixtures. so that it has been necessary to redetermine and readjust the proper oil mixture for each specific ore worked with.

I have discovered that the flotation process can be improved by the en'iployment of liquid distillates from gilsonite as flotation or frothproducing reagents. Not only do such ,c-ilsonite distillate reagents have good efficiency in flotation. but they areunique in their general suitability forthetreatment of metallic ores susceptible of being Application filed. November 10, 1920. Serial lilo. 423,152.

dealt with by flotation: in other words, they are practically auniversal flotation agent. They differ essentially from all oils hitherto used (singly or in admixture) in having inherently the ratio between saturated and unsaturated hydrocarbons proper for flotation purposes. The consumption of oils in flotation. is so large, moreover. that the applicability of a relatively cheap product such as gilsonite distillate to this use is of great economic importance, since it affords the industry a possibility of largely or entirely dispensing with the use of c'ristly agents such as pine oils. eucalyptus oil. etci, which are practically indispensable when petroleum and coal tar oils are employed for flotation. i

Gilsonite is a hard, brittle, shiny black bitumen which is found in large quantity in Utah, U. S. .53., and elsewhere. as veins in the earth, generally between. rocks, and is remarkably pure in its native state. Its specific gravity is about 1.04; the color of its powder is brown; it melts when heated. It has been used, (even in its native state) in, the manufacture of black varnishes and of rubber substitutes; also. by melting it or dissolving;- it in oils, for various other purposes.

Vl hen distilled, gilsonite yields from 8 to 10'}? of combustible and luminous gases and ammonia, to 7W4 of liquid hydrocarbons, and from to 30% of a residue of coke. The. liquid hydrocarbons obtained by distillation have a specific gravity of from .85 to and are decidedly liquid at'ordinarv normal atmospheric temperatures. They begin to boil at some 165" ll, (about (1.), and they all distill at temperatures"below some 750 1 (about 400 (1.). They it occurs Brazil from time to time on the body of vapor in the.

upper portion of the still, as Well as on the body of liquid beneath it. Excepting as there may be special occasion for distinguishing them, is here and hereinafter comprehend mingled gases and vapors under the single term vapor, for the sake of brevity. For

convenience, I refer to various stages of operations by the corresponding vapor temperatures, unless otherwise specially noted.) The effect of the progressive heating of the gilsonite is to gradually break it up and decompose 1t,- whence, mainly, the evolution of vapor. It is a diflicult matter "to describe the process, or to determine in what order various products are formed or come off, since the coming oil of particular products depends on the stability under heat of the highly complex chemical combinations amongst the constituents of gilsonite, as well as upon the boiling points of the products themselves. The matter is further complicated, no doubt, by the liberation, formatiou, and decomposition of intermediate products both in the body of liquid and in the body of vapor. However, the coming off of vapor from the still begins at a temperature of some 165 F., (about C.)

and continues up to or even beyond coking temperatures. The distillation may proceed, therefore. with evolution of gases and liquids, until the bottom of the still is a cherry red and the vapor temperature is some 750 l b, (about 400 (1). perature of the coke formed in the bottom of the still need not exceed some 850 F.

(about 455 g ll p to the point where the vapor temperature approaches some 550 F. (about 285 G), the distillation may be carried out as rapidly as the contents of the still can be-- made to absorb heat. At this point, however, some exothermic or other peculiar action'occurs, so that the evolution of vapor in the still tends to become excessively rapid.

Unless, therefore. the previous heating has been especially slow, it is advisable to reduce the application of heat very greatly as this critical point is approached, in order that undistilled liquid may not be carried over into the condenser, and clog it up so as to render it unusable. in practice, it

The maximum te1n-' will usually be found convenient to cut down the fire some 100 F. in advance of this temperature. Once this critical point is well passed, the fire'may be increased and the distillation pushed on as rapidly as de-' sired to its conclusion.

The distillation may be entirely dry; or, if preferred, live steam may be conducted through the gilsonite in the still during the distillation. Such employment of steam is advantageous, though not essential, to the process.

While the vapor coming off from the still may all be led into the iron pipe condenser, as above suggested, and all of the strictly vaporous portion thereof condensed and collected as a liquid, a slightly different procedure is preferable. A minor portion of the vapor is condensable at relatively high temperatures; and at the lower temperatures in the condenser (especially if water-cooled), the corresponding condensate is of such thick, gummy consistency that it would tend to clog it up. It is desirable, therefore, that this heavier portion of the normally liquid products be condensed and collected separately, without entering the condenser at all. This can advantageously be taken care of by making the pipe leading from the still to the condenser of substantial length and providing it with a trap. With this arrangement, the heavier portion of the normally liquid products will be condensed by the cooling effect of the at mosphere upon the pipe (which thus acts as a sort of auxiliary condenser), and will collect in the trap, whence itcan be drawn off from time to time and added to theliquid products drawn from the condenser itself. The trap also affords a measure of protection against the effects of too rapid heat ing at the critical temperature above mentioned. i

The truly gaseous portion of the distilla-' tion products will pass uncondensed through the condenser and be collected separately, in any suitable manner. The liquid condensate may. be collected in any kind of suitable receiver.

The distillate of liquid hydrocarbons thus obtained from gilsonite may be used ,in metallic separation by flotation without any change or any mixture of other oils. In practicing myotation process With it, I, therefore, add Such gilsonitic distillate to a watery, mixture consisting of a finely pulverized metallic ore or slime and an excess of water, contained in a suitable receptacle. The mixture being constantly agitated, with air or by mechanical means, the hydrocarbons cause a froth in and on the liquid which foams over the top ofthe vessel (or out of an openingin one side thereof, provided for this purpose), carrying with it the metallic portions of the ore under treatment and leaving thegangue behind. The amount of liquid hydrocarbon required is variable, dependingupon the kind of ore treated, but in general is from one-fourth of 1% to 1%.

The crude distillate obtained described aboie contains from 2% to 5% of water, which (though innocuous to its use as a flotation reagent) may readily be eliminated by settling cut in a settling tank. The distillate is a reddish brown oil with a green fluorescence; it is decidedly liquid at ordinary atmospheric or normal temperatures; is of about 0.875 specific gravity at F., (about 15 C); begins to boil near the lower limit (165 B, or about C.) of the temperature range mentioned above. and distills completely below the upper limit {some 750 F, or about 400 C.) of said ange; flashes in the air at ordinary tem- ,ratures; and contains, (as already mentioned), a very high percentage of unsaturated hydrocarbons, usually about 60%. It is immiscible and insoluble in water, butcompletely soluble in benzole and carbonbisulphide, and miscible in. all proportions with petroleum and petroleum products, and with turpentine and with pine oil.

\Vhile the crude primary gilsonite dis tillate obtained as described above. may he used directly as a flotation reagent, yet, if desired, certain light hydrocarbons that are otherwise very useful may be removed from the crude distillate Without impairing the fitness and advantages of the residue for flotation. For example, a dry redistillation or reduction may be carried out in a suitably heated steel still,the vapors coming oil up to some 600 1 (about 315 C.) vapor temperature being condensed, with incidental fractionation, if desired, and the residue of oil unvaporized at 60% F. Ibeing subsequently drawn off for use as flotation reagent without "further treatment of any sort.

I make no claim of novelty for the apparatus referred to in the above descrip- 7 tion of the production of gilsonitic distillate; on the contrary, practically any type of destructive distillation. apparatus may be employed which will produce such distillate from gilsonite. Neither do I here claim the distillation process described above, nor the gilsonitic distillates thereby produced, since all these and other matters here disclosed or referred to form the subject of my pending applications, Serial No. 195,721 of October 10, 1917 (above mentioned) and Serial No. 318,536 of August 19, 191%), entitled Gilsonite products and their manufacture.

Having thus described my invention, l claim:

The process of metallic separation, which consists in adding to a watery mixture containing finely pulverized ores or slimes a liquid hydrocarbon obtained from the de-I structive distillation of gilsonite and characterized by a very high percentage of unsaturated hydrocarbons; and aerating), the mixture, whereby themetallic portions of the ore are separated from the gangue.

In testimony whereof, I have hereunto signed my name at Maui-er, N. J., this 6th day of November, 1920.

CHARLES N. FORREST. 

